In the last few years, there has been continuous research to obtain the lightest possible thermoplastic container. Initially, light-weighting was studied at the level of the bottle/preform profile, without reducing the physical-mechanical behavior of the bottle. Later, light-weighting was focused on the neck of the bottle, reduced dimensions, wall thickness, thickness of the support ledge, and so forth. A known example is the change from PCO 1810 to PCO 19, to arrive finally to “PCO Corvaglia”. In this manner, global weight reduction has reached the actual limits. The need to use less material, for economical and environmental reasons, is becoming more pressing and imminent.
In some cases, very low weights have been developed. However, to obtain satisfactory mechanical behavior with these containers tricks, such as adding nitrogen are used. In fact once the container is opened it becomes uneasy to handle. In this context, emerged the necessity to obtained containers with good mechanical performance but light in weight.
A detailed analysis of the weight distribution of the lightest produced bottles with the lightest known necks demonstrated that the sections with the most material were the neck and the area under the support ledge. For example, some cases that were considered ranged from 40% to 26% of material accumulated in these sections. Therefore, an ultra light-weight neck (which maintains the necessary rigidity to maintain its shape during production of the container and to maintain the resistance in successive phases until the final use by the consumer) was developed without increasing the bottle body weight.
An excessive reduction in the weight of the neck, by reducing the width(s), in fact causes problems during the heating and blowing phases of the process. For example, the neck or neck support ledge deforms, which creates complications in successive phases of bottling (e.g., transportation on guides, filling, capping, and palletizing). The neck can be deformed even in these last steps.
The new preform/mould profile permits the reduction of neck widths to less than the actual limits, which, until now, have been considered necessary to avoid the oval deformation caused by the effect of the major radial resistance of this geometry.
In this way, a bottle with a weight reduction of 30-40%, with respect to those considered in the preliminary analysis, was developed. Another bottle, was also developed that was an additional 14% lighter. In these containers, taking into account the initial considerations, only 17% of the weight of the material was accumulated in the neck and under the support ledge.
Another aspect to consider is that the caps are produced with widths that resist neck deformation. This invention, which maintains the rigidity, also permits the reduction cap weight.
The particular geometry of the neck profile and of the area under the support ledge, allowing the possibility to increase the distance z, benefits the capping process and transport of the bottle. The greater the dimension is, the easier the transportation due to the greater surface area. The increase of this dimension also facilitates the capping process, allowing mandrels to easily grip the support ledge.
In the case of geometries of the “swerve” type (FIG. 1) the dimension y is about 20 to 100% greater than the dimension z of the classical cases (FIG. 2) depending on the type of neck. It can also be confirmed that part of the available surface y of the invention allows for the reduction of the diameter of the support ledge, thus obtaining a further reduction of the neck weight.
The increase in dimension from z to y facilitates the application of typical handles in the larger formats due to more space being available, and improving sturdiness through the lighter weight of the neck.
Another important aspect of this invention is that it is suitable for existing lines consisting of blowing machines, transportation lines and filling machines. This invention can also stimulate innovations in the projection and development of new systems. The various types of moulds in use today can be used by simply substituting the collars where the support ledge is held.